Method of lining concrete pipes



March l 1938. F. KLINGENsMn'l-l METHOD OF LINING CONCRETE PIPES FiledDec. 16, 193

ATTORN EYS Patented Mar. l, 1938 UNITED STATESA PATENT OFFICE 2,109,644y METHOD oF uNlNG CONCRETE PIPEs Y Frank L. Klingensmith, BloomfieldHills, Mich. Application December 1s, `1935, serial No. 54,611

a claims. -(ci. :i1-7o) The present invention relates to a method oflining concrete pipes and the like whereby such pipes may be used forconveying liquids containing acids and other destructive materials,sometimes present in sewage, which attack, and in time destroy, the`walls of concrete pipe.

The primary object of the present invention is to provide for the liningof a concrete pipe with a coating material of which the essentialconstituent is coal tarand other resinous materials with properties toincrease elasticity, resist attack by acids and other erosive materials.'I'his material is available on the market and is commercially known aswater works enamel and the invention pertains more particularly to themethod of treating the pipe prior to the application of thismaterial andto the particular method of applying the material.

The invention is more fully disclosed with reference to the accompanyingdrawing, in which Fig. 1 is a diagrammatic vertical section ofk a plantfor treating pipes according to the present method;

Fig. 2 is a plant, and

Fig. 3 'is a transverse section of a pipe.

Like characters of reference are employed throughout to designatecorresponding parts.

Referring to Fig. 1 there is illustrated mechanism l, well known in theart and therefore not shown in detail here, for receiving and rotatingcylindrical forms or molds 2. As the mechanism .l rotates the formconcrete is poured thereinto and is distributed throughout the form bythe plan, partly in cross section, of the centrifugal forces created byrotation thereof. As

the form is rotated the concrete therein is trowelled to provide thepipe, thus formed, with'a smooth inner surface, free from loose scaleand slurry, after which the pipe is removed from the mechanism I and isplaced while still in the form or mold 2, in a kiln 3 at a temperatureof approximately 120 F. After beingproperly cured in the kiln 3 thepipe, still in the form vor mold 2, is placed in a dry atmosphere whereit is allowed to stand for a period 'of time approximating twenty-fourhours, after which it is ready for the first primer treatment accordingto the present invention. However, before being treated with primeraccording to the present method all loose shale orl slurry formed on theinner surface of the pipe I during the curing is completely removed bythe use of a scraping implement or a Wire brush. The

`surface is cleaned after wire brushing with dry compressed air, carebeing exercised that the air so used is free from oil.

inner surface of the tubeeither by. brush or spray, 10`

care being exercised to provide equal distribution thereof and to avoidflooded areas which will not dry properly. The coverage of primer variessomewhat, according to the particular method of application, but it hasbeen found that ordinarily l5 a coverage of three to four hundred squarefeet per gallon of primer provides for satisfactory results.

After a period of time, not-less than six hours and not more thanseventy-two hours, a second 20 coat of primer is applied. A convenientprocedure, under normal weather conditions,is to apply the rst, thinnedcoat of primer in the morning and from six to eight hours later, toapply the second coat. The following day the primer is 25 usuallysufllciently dry for the enamel application to be presently described.

'I'he second coat ofl primer consists of regular water works primer (ascommercially known) without the addition of thinner as in the oase with30 the rst coat. 'I'he dryness of the second coat of primer beforeapplication of the enamel may be determined by sliding the hand undermoderately hard pressure over the surface of the primer. If the primerhas set so that it will not deform or 35 rub off on the hand it issufliciently dry for the purposes of the invention.

The enamel, which provides the erosion resisting coating when subjectedto contact with liquids containing acids and other erosive materials 40is applied centrifugally in much the same manner as the concrete of thepipewas originally placed in theform. For this purpose the pipe, stillin the form 2 is placed on the'mechanism 4 for rotating the form. Theenamelconsisting essen- 45 tially of coal tar and other resinousmaterials with properties to increase elasticity and to resist attack byacids andpther erosive materials is` heated to a temperature of 425 F'.to 475 F. and

'is placed in a trough which extends throughout 50 enamel is distributedevenly throughout the enn ameter. After application of sufficient enamelto f tire length of the pipe and the trough is positioned with itsstraight edge as near as is practical to the downwardly moving internalsurface of the pipe. The trough should be uniformly heated during theenamel application.

During the pouring of the enamel into the pipe the latter is beingrotated and it has been found that a peripheral speed of one thousand tofifteen hundred feet per minute is satisfactory for pipes forty-eight toeighty-four inches in diform a' coating approximately one quarter of aninch in thickness rotation of the pipe is continued until the enamel hasbecome firmly bonded to the pipe surface and has set or hardenedsufficiently to avoid sagging thereof when the rotation is stopped.

The enamel, being poured on the pipe surface at a temperature between425 and 475 and in suiiicient quantity to provide a layer approximatelyone quarter of an inch thick, causes the Wall of the pipe to be heated,and it also heats the primer to a temperature higher than its nor-l malmelting point so that the enamel uniformly bonds therewith. The enamelsolidies at a temperature of approximately 200 F. and the fact that itis'poul'ed heats the walls provides for a comparatively slow coolingaction. That is to say, the pipe wall retains the heat longer than theenamel does, and the enamel is maintained liquid by the heated wall ofthe pipe for a period of time whereby the centrifugal action removes allridges, surface irregularities and blisters which result from airpockets or bubbles in the enamel.

Before shipping or storing the lined pipe out of doors where it mightrest in the rays of the sun the inner surface is completely whitewashed.The purpose o f the whitewash is to minimize the excessive'temperaturewhich results when a black surface is exposed to the sun, due to theinability a't a temperature whereby it of the black surface to reflectthe sun's rays. Such treatment is deemed important in the present methodbecause the enamel employed is black in color and excessive temperatureswould cause the lining to soften and run.

Referring to Fig. 3 wherein a completed pipe is shown in cross section,the numeral 6 designates the concrete pipe, 1 the iirst primer, 8 thesecond primer and 9 the enamel lining.

Although a specific embodiment of the invention has been illustrated anddescribed it will be understood that various changes may be made withinthe scope of the appended claims without departing from the spirit ofthe invention, and such changes are contemplated.

f What I claim is: l

1. The method of lining a kiln dried and subsequently cooled pipe whichconsists in, applying a coal tar base enamel at temperatures from 425475F. to a primed surface of a concrete pipe while rotating said pipe at arate of 1000 to 1500 peripheral feet per minute, and cooling said enamelto atmospheric temperature.

2. The method of lining a kiln dried and subsequently cooled pipe whichconsists in, applying a coal tar base enamel at temperatures from425-475 Ffto a primed surface of a concrete pipe while rotating saidpipe at a rate of 1000 to 1500 peripheral feet per minute, and rotatingsaid pipe while cooling said enamel to the temperature of said pipe.

3. The method of lining a kiln dried and subsequently cooled pipe whichconsists in, applying a coal tar base enamel at temperatures from 425475F. to a primed surface of a concrete pipe while rotating said pipe at arate of 1000 to 1500 peripheral feet per minute, rotating said pipewhile cooling said enamel to the temperature of said pipe, andsubsequently covering said enamel with whitewash.

FRANK L. KLINGENSMITH.

